1. Field of the Invention
The present invention pertains to an apparatus adapted to mount on a fluid transmission line for inserting a flexible bag into the line interior wherein the bag is filled with liquid and frozen to form a flow stopping plug. One embodiment of the apparatus includes an elongated tubular probe member comprising a heat exchanger for freezing and thawing the liquid within the bag interior.
Background
The above-referenced patent pertains to a method and apparatus for repairing fluid transmission lines and the like by inserting a flexible bag into the interior of the line, filling the bag with liquid and freezing the liquid to form a substantially fluid-tight plug in the line adjacent to a point wherein the line requires repair or replacement of a line section for various purposes.
In the development of the invention described in the above-referenced patent, it has been determined that it is desirable to be able to accelerate the liquid freezing and thawing process during the procedure for repairing or replacing the line by exchanging heat with the liquid in the bag as rapidly as possible. Since the bag is disposed within the interior of the transmission line the provision of a cryogenic flud circulation chamber on the exterior surface of the line requires some time to freeze the liquid in the bag. Moreover, in certain environments such as submarine pipelines, the deployment of the cryogenic fluid circulation casing for encircling the pipeline to form the freeze plug is a difficult exercise and if fluid can be frozen and thawed in the bag from a heat exchanger deployed within the bag several advantageous are realized. In any event, it is desirable to be able to bring about the freezing and thawing of the liquid within the bag as well as to provide for easy insertion of and removal of the bag from the line interior. To this end there has been a need for certain improvements in apparatus for inserting flexible bags into the interior of various types of fluid transmission lines. Foremost among these needs, is perhaps the need to provide a greater rate of heat exchange between the liquid in the bag and the fluid being used to cool or heat the liquid as mentioned above. In other regards there has been a need for apparatus which is easy to operate in the process of inserting the bag into the line interior, inserting and removing a heat exchanger with respect to the interior of the bag, and removing the bag from the line interior when the operation requiring the flow stopping plug has been completed.
There has also been a need for an improved apparatus for inserting and withdrawing flexible bags with respect to the interior of a fluid transmission line, wherein the apparatus is adapted for conditions wherein relatively high fluid pressures exist within the line interior both during the bag insertion process and thereafter while the apparatus is mounted on the transmission line and connected to the bag.
The present invention provides for a flexible bag insertion apparatus for forming a flow stopping plug in a fluid transmission line or the like which provides certain unique features and solves several problems present in the art.